The role of proficiency in the interlanguage speech intelligibility benefit

Previous research indicates nonnative listeners may have an advantage at understanding nonnative speech of talkers with the same L1 due to shared interlanguage knowledge. The present study offers a comprehensive analysis of various factors that may modulate this advantage, including the proficiency of interlocutors, the mapping of phonemes between the L1 and L2, and the acoustic properties of the phonemes. Accuracy scores on a lexical decision task were used to identify whether native Mandarin learners of English are better than native English listeners at perceiving Mandarin-accented English speech, as well as whether they are better at perceiving Mandarin-accented English compared to native English speech. Results indicated an overall native English interlocutor advantage, an advantage for common-phoneme over unique-phoneme words in nonnative speech, and some evidence of gradience in ISIB effects based on the proficiency of talkers and listeners. No strong relationship between type of English input (native or accented) and the ability to understand Mandarin-accented English speech was found. The nonnative listener advantage at perceiving nonnative speech is relatively small and depends on various factors, including listener proficiency, speaker proficiency, phoneme characteristics, and the acoustics of specific speech tokens.